Fault analysis of Slow speed

Computer network failure is unavoidable. The network fault diagnosis is the important work of network management after the campus network is built and run. Generally when the network occurs information is not available, can not browse the Web, and other connectivity failures, the phenomenon is relatively clear, easy to observe and locate the fault point, such a fault is not difficult to solve. But the most troubling thing is that the internet is a pass, but the network speed slows down. When faced with this kind of "soft" fault for the first time, some people will be helpless. This article introduces the causes of such "soft" failures and their elimination methods, so as to improve the ability of dealing with practical problems.

One, network cable problems caused by slow speed

We know that twisted-pair wires are tightly twisted and together by four pairs of lines to reduce crosstalk and background noise. At the same time, only 1, 2 and 3, 64 lines of twisted pair are used in the T568A standard and the T568B standard, where 1, 2 are used for sending, 3, 6 is used for reception, and 1, 2 must come from a winding pair, 3, 6 must come from a revolve pair. Only in this way can the maximum avoid crosstalk and ensure data transmission. In practice, I found that not according to the correct standard (T586A, t586b) The production of network cable, there are a lot of hidden dangers. The performance is: one kind of situation is when starts to use the network speed is very slow, the other kind of situation is starts the net speed to be normal, but after some time, the net speed slows down. The latter situation is evident on desktop computers, but the speed at which the computer is checked with a laptop is normal. For this problem I have been found for many years, due to not according to the correct standard made by the network cable caused by slow speed and the quality of the network card. General desktop computer network card performance is not as good as notebook computer, therefore, in the use of the Exchange method to troubleshoot, the use of notebook computers to detect the normal speed of the network does not rule out the existence of the problem. We are now required to press T586A, t586b Standard to suppress the network cable, in the detection of faults can not be used to replace the desktop computer notebook computer.

Second, the network has a circuit to slow the speed

This phenomenon rarely occurs when the number of nodes involved in the network is not many and the structure is not very complex. However, in some more complex networks, there are often redundant lines, such as inadvertently connected to form a circuit. For example, cable from the network Center to a computer room, and then from the computer room to the second room computer. At the same time from the network Center and a standby line directly connected to the computer room two, if the several lines connected at the same time, the formation of the circuit, the packet will continue to send and verify data, thus affecting the overall speed. This is a difficult situation to find. In order to avoid this situation, we must be in the laying of the network of good habits: network cable marked on the label, there is a standby line of the place to do a record. When such a failure occurs, it is generally used in a step-by-step approach to partition segmentation.

Third, network equipment hardware failure caused by the broadcast storm caused by slow speed

As the main means of discovering unknown devices, broadcasting plays a very important role in the network. However, as the number of computers in the network increases, the number of broadcast packets will increase dramatically. When the number of broadcast packets reaches 30%, the transmission efficiency of the network will decrease obviously. When the NIC or network device is damaged, the broadcast packet will be sent continuously, causing the broadcast storm and paralyzing the network communication. Therefore, when the network equipment hardware failure will also cause slow speed. When you suspect such a failure, you can first replace a hub or switch with a replacement to troubleshoot a hub device failure. If these devices do not malfunction, turn off the hub or switch power, DOS under the "Ping" command to the computer involved in one test, to find a faulty network card computer, replace the new network card can restore normal speed. Network adapters, hubs, and switches are the most likely devices to cause slow internet speed.

Four, the network of a port to form a bottleneck leading to slow speed

In fact, routers WAN and LAN ports, switch ports, hub ports, and server network cards can become network bottlenecks. When the speed is slow, we can use the network management software to view the data traffic of routers, switches and server ports during the peak period, and can also use the netstat command to count the data traffic of each port. This confirms the location of network data flow bottleneck and tries to increase its bandwidth. Many specific methods, such as replacing the server network card for 100M or 1000M, installing multiple network cards, dividing multiple VLANs, changing the router configuration to increase bandwidth, etc., can effectively alleviate the network bottleneck, can maximize the speed of data transmission.

Five, the worm's influence causes the network speed to become slow

The worm virus which is distributed through e-mail is more and more serious and harmful to the network speed. The virus causes infected users to keep sending emails as soon as they surf the internet, and the virus chooses random documents in the user's personal computer to attach to the random address of the user's address book to send mail. Hundreds of such spam messages are queued to be sent out, and some are returned to heap on the server in batches. Cause individual backbone of the internet appears obvious congestion, network speed significantly slowed down, so that the LAN nearly paralyzed. Therefore, we must upgrade the anti-virus software in time, the computer also need to upgrade in time, install the system patch, while unloading unnecessary services, shut down unnecessary ports, in order to improve the security and reliability of the system.

In a word, the application of computer network is more and more extensive, it is very important to improve the management level of campus network, keep learning, pay attention to the close combination of theoretical knowledge and practical operation.